#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <sys/socket.h>

#define BUF_SIZE 30
void error_handling(char* message);
void read_childproc(int sig);

int main(int argc, char* argv[]) {
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_addr, clnt_addr;

    pid_t pid;
    struct sigaction act;
    socklen_t clnt_addr_size;
    int str_len, state;
    char buf[BUF_SIZE];
    if (argc != 2) {
        printf("Usage: %s <port> \n", argv[0]);
        exit(1);
    }

    act.sa_handler = read_childproc;
    sigemptyset(&act.sa_mask);
    act.sa_flags = 0;
    state = sigaction(SIGCHLD, &act, 0);

    serv_sock = socket(PF_INET, SOCK_STREAM, 0);
    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_addr.sin_port = htons(atoi(argv[1]));

    if (bind(serv_sock, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
        error_handling("bind() error");
    if (listen(serv_sock, 5) == -1)
        error_handling("listen() error");

    while (1) {
        clnt_addr_size = sizeof(clnt_addr);
        clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_addr, &clnt_addr_size);
        if (clnt_sock == -1)
            continue;
        else 
            puts("new client connected...");
        pid = fork();
        if (pid == -1) {
            close(clnt_sock);
            continue;
        } 
        if (pid == 0) /*子进程运行区域*/
        {
            close(serv_sock);
            while ((str_len = read(clnt_sock, buf, BUF_SIZE)) != 0) {
                write(clnt_sock, buf, str_len);
            }
            close(clnt_sock);
        }
        else 
            close(clnt_sock);
    }
    close(serv_sock);
    return 0;
}

void read_childproc(int sig) {
    pid_t pid;
    int status;
    pid = waitpid(-1, &status, WNOHANG);
    printf("remove proc id: %d \n", pid);
}

void error_handling(char* message) {
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}